1. Field of the Invention
The present invention relates to a head drum assembly and a tape drive using the same. More specifically, the invention relates to the art for preventing crosstalk between different transmission systems in a rotary transformer and improving mounting accuracy of the rotary transformer.
2. Description of the Related Art
With recent trend of a multi-channel of a magnetic head, a head drum assembly provided with plural sets of rotary transformers.
For example, Japanese Patent Application Laid-Open No. H05-274603 shows in FIG. 5 a head drum assembly provided with two sets of rotary transformers as a prior art example.
In the head drum assembly of the above publication, a rotor is supported on the upper end of a rotary shaft supported rotatably on a lower stator, and an upper stator is supported in a cantilevered manner on the extreme end of a support column screwed to the outer peripheral part of the lower stator.
According to the head drum assembly as described above, a set of rotary transformers and a separate set of rotary transformers can be arranged on the opposed surface between the lower stator and the rotor and on the opposed surface between the upper stator and the rotor, respectively, and at least two sets of rotary transformers can be disposed on a single head drum.
In the head drum assembly as described above, since the rotary transformer can be composed of two systems, for example, crosstalk between transmission of reproducing signals and transmission of recording signals can be prevented.
However, in the head drum assembly as described above, since the support column supporting the lower stator is essentially provided in order to lock the upper stator, there causes a problem that the high cost is brought forth, the mounting accuracy of the rotary transformer is poor, and the performance of the rotary transformer lowers.
That is, since the column supporting the lower stator is essentially provided in order to lock the upper stator, the number of parts increases accordingly, and the mounting accuracy of the upper stator lowers unless the dimensional accuracy of the column is enhanced. Particularly, since the upper stator is supported in a cantilevered manner on the support column, the mounting accuracy of a coil plate on the stator side constituting the rotary transformer becomes worsened unless the accuracy of a mounting surface is improved. Since a gap between the stator coil plate opposed to the rotary transformer and a rotor coil plate is of order of scores of xcexcm, the dimensional accuracy need be much improved, resulting leads higher cost.
Further, a gap between the stator coil plate opposed to the rotary transformer and a rotor coil plate is of order of scores of xcexcm, an area of the mounting surface of the upper stator supported in a cantilevered manner is small, and such supporting is done by screwing, because of which a fine gap between the opposed stator coil plate and the rotor coil plate is different in side near the support column from the side away from the support column according to a tightening force of a screw.
In Japanese Patent Application Laid-Open No. Hei 5-274603, this problem is solved by two sets of so-called cylindrical rotary transformers which are arranged axially concentrically. In this case, however, the rotary transformers are laminated in an axial direction of the drum, and the height of the drum becomes higher, which is disadvantageous for miniaturization of a tape drive.
It is therefore an object of the present invention to realize a small type head drum assembly and a tape drive which prevents crosstalk between different transmission systems in a rotary transformer and improves the mounting accuracy of the rotary transformer.
For solving the aforementioned problem, a head drum assembly according to the present invention comprises, a fixed shaft secured to a lower stator; and a rotor having a motor unit and a magnetic head; an upper stator disposed axially with the rotor held and secured to the shaft, and rotary transformers separately provided between the rotor and the stator.
The present invention further provides a tape drive comprising a head drive in which a magnetic head is provided on a rotor and a magnetic tape is wound at a predetermined angle, a guide pin for drawing out a magnetic tape from a tape cassette and winding the drawn magnetic tape about the head drum assembly to form a tape pass, a reel bed for supporting a reel of a tape cassette, and a capstan shaft for traveling a magnetic tape in cooperation with a pinch roller, wherein the head drum assembly comprises, a fixed shaft secured to a lower stator and a rotor having a motor unit and a magnetic head; an upper stator disposed axially with the rotor held and secured to the shaft, and rotary transformers separately provided between the rotor and the stator.
Accordingly, in the head drum assembly and the tape drive using the same, plural sets of rotary transformers can be loaded at a distance axially, and signal transmission systems of different transmission systems can be disposed separately, thus enabling prevention of crosstalk.
Further, the shaft is locked, the rotor is rotatable around the shaft, and the upper and lower stators are fixedly supported. Therefore, the rotor and the stator can be mounted with the shaft as a reference, and the mutual mounting accuracy can be improved whereby the performance of the rotary transformer is not deteriorated, thus enabling provision of a small and high performance rotary transformer.
In the present invention, in the plural systems of the rotary transformers which are of a plane type, the head drum assembly can be constituted to be a small type, and the manufacturing cost can be reduced as compared with the cylindrical rotary transformer.
Further, in the present invention, in the arrangement in which the rotary transformer of the transmission system of recording signals and the rotary transformer of the transmission system of reproducing signals are separated in separated set, crosstalk of signals of the recording system and the reproducing system can be prevented, and particularly, in a rotary drum for a data streamer, the RAW (Read After Write) function can be realized easily.
Furthermore, in the present invention, in the arrangement in which at least one set of rotary transformers is larger in diameter than the outside diameter of a rotor, the large opposed surface of the rotary transformer can be employed for the outside diameter of the rotor, and crosstalk between the transmission systems can be prevented accordingly.